Treatment element for treating material in a multi-shaft worm machine and multi-shaft worm machine

ABSTRACT

A treatment element to treat material in a multi-shaft worm machine has an outer contour with at least one outer contour portion, the associated evolute of which is a quantity of at least three points, each of the points lying outside the longitudinal axis and within the outer radius of the treatment element and two respective adjacent points having a spacing from one another, which is less than half the core radius. The treatment element ensures high flexibility during the adjustment of shear and/or extensional flows on the material to be treated.

REFERENCES TO RELATED APPLICATIONS

This application claims the priority of European Patent Application, Serial No. 09 012 358.9, filed Sep. 29, 2009, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein.

FIELD OF THE INVENTION

The invention relates to a treatment element for treating material in a multi-shaft worm machine, in particular in a two-shaft worm machine, comprising

-   -   a longitudinal axis M,     -   a respective core radius R_(i) having the longitudinal axis M as         the centre point and an outer radius R_(a),     -   an outer contour A(φ) running about the longitudinal axis M,         wherein     -   φ is the angle about the longitudinal axis M and     -   R_(i)≦D_(A)(φ)≦R_(a) applies to a spacing D_(A)(φ) of the outer         contour A(φ) from the longitudinal axis M.

Furthermore, the invention relates to a multi-shaft worn′ machine, in particular a two-shaft worm machine with

-   -   a housing,     -   at least two housing bores, which penetrate one another and are         parallel to one another,     -   at least two shafts arranged concentrically in the housing         bores,         -   which are rotatably drivable about associated rotational             axes, in particular are rotatably drivable in the same             direction, and         -   which have an axial spacing a of the rotational axes,         -   a plurality of treatment elements for treating material,         -   which are non-rotatably arranged one behind the other in an             axial direction on the at least two shafts, and         -   which are configured to tightly mesh with one another.

BACKGROUND OF THE INVENTION

A two-shaft worm machine with single-threaded treatment or worm elements is known from DE 1 180 718 A. The outer contour of the worm elements is composed of circular arcs in cross-section. The active flank located in the rotational direction has an outer contour, which is composed of three circular arcs, the centre points of which are either located on the outer radius or on the longitudinal axis of the worm elements. The drawback is that the worm elements only allow a small flexibility in the adjustment of the shear and/or extensional flows acting on the material to be processed.

SUMMARY OF THE INVENTION

The invention is based on an object of developing a treatment element of the generic type in such a way that a high flexibility is provided in the adjustment of the shear and/or extensional flows acting on the material to be processed.

This object is achieved by a treatment element, in which

-   -   the outer contour A(φ) has at least one outer contour portion         A(Δφ), which runs along an angle portion Δφ,         -   which has a continuously changing spacing D_(A)(Δφ) from the             longitudinal axis M, wherein R_(i)<D_(A)(Δφ)<R_(a), and         -   which has an associated evolute E,             -   which is a quantity of n points P(i) where i=1 to n and                 n≧3,             -   wherein each of the points P(i) lies outside the                 longitudinal axis M and within the outer radius R_(a),                 and             -   wherein two respective adjacent points P(i) and P(i+1)                 have the spacing Δr(i) from one another, which is less                 than R_(i)/2.

It was recognized according to the invention that the treatment elements known from the prior art, with the same ratio of the outer radius to the core radius, have the same angle of intersection of the active flank curve with the crest curve. The inner radius of the housing bores is greater by the radial play than the outer radius of the treatment elements. A geometrically similar form of the wedge between the inner contour of the housing and the active flank curve is therefore always produced with a constant ratio of the radial play to the outer radius. As the shear and/or extensional flows prevailing in the wedge substantially depend on the geometrical form thereof, they can only be adjusted by the angle of intersection of the active flank curve with the crest curve. As the angle of intersection only depends on the ratio of the outer radius to the inner radius, the adjustment of the shear and/or extensional flows is only possible to an extremely limited extent by means of the geometry of the wedge.

In comparison, the treatment element according to the invention—viewed in cross section or in a cross sectional projection—has at least one outer contour portion A(Δφ_(j)), the associated evolute E_(j) of which is a quantity of n points P(i) wherein i=1 to n and n≧3, in particular n≧4 and, in particular n≧5, wherein each of the points P(i) lies outside the longitudinal axis M of the treatment element and within the outer radius R_(a) thereof. Two adjacent respective points P(i) and P(i+1) have a spacing Δr(i) from one another, which is smaller than R₁/2, in particular smaller than R_(i)/4, in particular smaller than R₁/6, and in particular smaller than R₁/8. Adjacent points P(i) and P(i+1) belong to adjacent involute curves E′(i) and E′(i+1). The involute curves E′(i), wherein i=1 to n together form the outer contour portion A(Δφ_(j)) belonging to the evolute E_(j).

The index j characterizes the number of evolutes. The at least one outer contour portion A(Δφ_(j)) forms at least one part of a flank of the treatment element, the associated wedge being flexibly adjustable by means of the type and arrangement of the evolute E_(j). Correspondingly, the shear and/or extensional flows that can be produced by the treatment element can be flexibly adapted to the material to be treated by the means of the type and arrangement of the evolute E_(j).

The evolute E_(j) of the associated outer contour portion A(Δφ_(j)) running in a plane is the location or the curve of the centre points of curvature or the centre points of the circle of curvature. The outer contour portion A(Δφ_(j)) belonging to the evolute E_(j) is also called the involute. A notional rod with the length of the axial spacing a is unwound on the evolute E_(j) to construct the outer contour, the first rod end defining the outer contour portion A_(i)(Δφ_(ji)) of one treatment element and the second rod end defining an associated outer contour portion A_(i+1) (Δφ_(ji+i)) of the further treatment element, which tightly mesh with one another when installed in a multi-shaft worm machine.

A high measure of degrees of freedom for the construction of the treatment element according to the invention is provided by the type, arrangement and number of evolutes so the outer contour portions (Δφ_(j)) can be varied with respect to their curvature, length and their angles of intersection over broad ranges. The wedges between the flanks and the inner contour of the housing can therefore be extremely flexible in design. As the shear and/or extensional flows prevailing in these wedges substantially influence the quality of the material to be processed, the quality can be optimized by the treatment element according to the invention and adapted to predetermined requirements. The at least one outer contour portion A(Δφ_(j)), in this case, in particular forms a part of the active flanks lying in the rotational direction.

The treatment element may be configured as a kneading element or kneading disc and have a constant outer contour in the direction of the longitudinal axis M. A plurality of kneading elements may be assembled with different offset angles about the longitudinal axis M with respect to kneading blocks. The kneading blocks may be produced in one part or be assembled from individual kneading elements.

Furthermore, the treatment element can be configured as a worm element, the outer contour of which is screwed in the direction of the longitudinal axis M by a constant and/or continuous function. The screwing can basically take place in the two rotational directions about the longitudinal axis M, so the worm element selectively has a conveying or retaining effect. Depending on the geometry of the worm element, the outer contour can optionally be understood as a cross sectional projection.

Furthermore, the treatment element may be configured as a transition element, which, in the direction of the longitudinal axis M, has a starting outer contour and an end outer contour, which are different, and change in the direction of the longitudinal axis M according to a continuous function in such a way that the starting outer contour continuously passes into the end outer contour.

The treatment element according to the invention can therefore be used with associated further treatment elements in any tightly meshing multi-shaft worm machines, in particular in two-shaft worm machines which can be rotatably driven in the same or opposite directions. The adjacent, tightly meshing treatment elements in this case form a treatment element group, the treatment elements of which were constructed by unwinding the notional rod of the length a on a common evolute E_(j) or a plurality of common evolutes E_(j).

The invention is furthermore based on the object of developing a multi-shaft worm machine of the generic type in such a way that a high flexibility is produced in the adjustment of the shear and/or extensional flows acting on the material to be processed.

This object is achieved by a multi-shaft worm machine having, in which

-   -   at least two treatment elements arranged directly next to one         another are configured such that each treatment element         comprises         -   a longitudinal axis M,         -   a respective core radius R_(i) having the longitudinal axis             M as the centre point and an outer radius R_(a),         -   an outer contour A(φ) running about the longitudinal axis M,             wherein             -   φ is the angle about the longitudinal axis M and             -   R_(i)≦D_(A)(φ)≦R_(a) applies to a spacing D_(A)(φ) of                 the outer contour A(φ) from the longitudinal axis M,     -   wherein         -   the outer contour A(φ) has at least one outer contour             portion A(φ), which runs along an angle portion A_(T),             -   which has a continuously changing spacing D_(A)(Δφ) from                 the longitudinal axis M, wherein R_(i)<D_(A)(Δφ)<R_(a),                 and             -   which has an associated evolute E,                 -   which is a quantity of n points P(i) where i=1 to n                     and n≧3,                 -   wherein each of the points P(i) lies outside the                     longitudinal axis M and within the outer radius                     R_(a), and                 -   wherein two respective adjacent points P(i) and                     P(i+1) have the spacing, and         -   the sum of the core radius R_(i) and the outer radius R_(a)             substantially equals the axial spacing a.

By means of the at least two treatment elements according to the invention, the wedges between the flanks and the inner contour of the housing may be flexibly varied, whereby the shear and/or extensional flows exerted can be optimally adapted to the material to be processed. The at least two treatment elements are configured and arranged in such a way that they tightly mesh and form a corresponding treatment element group. This is achieved in that the sum of the outer radius R_(a) and the core radius R_(i) substantially corresponds to the axial spacing a. Substantially this means that the axial retraction b, which is conventional in practice, is disregarded. If the axial retraction b is taken into account, the sum of the outer radius R_(a) and the core radius R_(i) corresponds to the difference of the axial spacing a and the axial retraction b.

The at least two treatment elements of the treatment element group were constructed on at least one common evolute E_(j) by unwinding a notional rod with the length of the axial spacing a or the axial spacing a less the axial retraction b.

Depending on the type, arrangement and evolute E_(j), the treatment elements of the treatment element group may be symmetrical, for example axially and/or rotationally symmetrical, or non-symmetrical and/or congruent or non-congruent. Moreover, the at least two treatment elements may be developed in accordance with the configurations according to the invention.

Further features, details and advantages of the invention emerge from the following description of a plurality of embodiments with the aid of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of a two-shaft worm machine configured as a two-shaft extruder according to first embodiment,

FIG. 2 shows a horizontal part longitudinal section through the two-shaft worm machine in FIG. 1,

FIG. 3 shows a vertical cross section through the two-shaft worm machine according to the section line in FIG. 1 with two tightly meshing treatment elements configured as kneading elements in a first rotational position,

FIG. 4 shows a vertical cross section through the two-shaft worm machine in accordance with the section in FIG. 1 with two tightly meshing treatment elements configured as kneading elements in a second rotational position,

FIG. 5 shows a perspective view of a plurality of treatment elements according to FIG. 3,

FIG. 6 shows a construction diagram to illustrate a first construction step of treatment elements in FIG. 3,

FIG. 7 shows a construction diagram to illustrate a second construction step of the treatment elements in FIG. 3,

FIG. 8 shows a construction diagram to illustrate a third construction step of the treatment elements in FIG. 3,

FIG. 9 shows a perspective view of a plurality of tightly meshing treatment elements configured as worm elements according to a second embodiment,

FIG. 10 shows a vertical cross section according to FIG. 3 with treatment elements according to a third embodiment,

FIG. 11 shows a construction diagram for illustrating the construction steps of the treatment elements in FIG. 10,

FIG. 12 shows a vertical cross section according to FIG. 3 with treatment elements according to a fourth embodiment,

FIG. 13 shows a construction diagram for illustrating a first construction step of the treatment elements in FIG. 12,

FIG. 14 shows a construction diagram to illustrate a second construction step of the treatment elements in FIG. 12,

FIG. 15 shows a construction diagram to illustrate a third construction step of the treatment elements in FIG. 12,

FIG. 16 shows a vertical cross section according to FIG. 3 with treatment elements according to a fifth embodiment,

FIG. 17 shows a vertical cross section in accordance with FIG. 3 with treatment elements according to a sixth embodiment,

FIG. 18 shows a vertical cross section according to FIG. 3 with treatment elements according to a seventh embodiment,

FIG. 19 shows a vertical cross section according to FIG. 3 with treatment elements according to an eighth embodiment,

FIG. 20 shows a vertical cross section according to FIG. 3 with treatment elements according to a ninth embodiment,

FIG. 21 shows a vertical cross section according to FIG. 3 with treatment elements according to a tenth embodiment,

FIG. 22 shows a vertical cross section according to FIG. 3 with treatment elements according to an eleventh embodiment,

FIG. 23 shows a vertical cross section according to FIG. 3 with treatment elements according to a twelfth embodiment,

FIG. 24 shows a vertical cross section according to FIG. 3 with treatment elements according to a thirteenth embodiment,

FIG. 25 shows a vertical cross section according to FIG. 3 with treatment elements according to a fourteenth embodiment,

FIG. 26 shows a vertical cross section according to FIG. 3 with two-threaded treatment elements according to a fifteenth embodiment,

FIG. 27 shows a construction diagram to illustrate the construction steps of the treatment elements in FIG. 26,

FIG. 28 shows a vertical cross section according to FIG. 3, with two-threaded treatment elements according to a sixteenth embodiment,

FIG. 29 shows a vertical cross section according to FIG. 3, with two-threaded treatment elements according to a seventeenth embodiment,

FIG. 30 shows a vertical cross section according to FIG. 3, with three-threaded treatment elements according to an eighteenth embodiment,

FIG. 31 shows a vertical cross section according to FIG. 3, with single-threaded treatment elements according to a nineteenth embodiment,

FIG. 32 shows a construction diagram to illustrate the construction steps of the treatment elements of FIG. 31,

FIG. 33 shows a vertical cross section accord ng to FIG. 3, with single-threaded treatment elements according to a twentieth embodiment,

FIG. 34 shows a construction diagram to illustrate the construction steps of the treatment elements in FIG. 33, and

FIG. 35 shows a vertical cross section according to FIG. 28, with eccentrically arranged treatment elements according to a twenty first embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the invention will be described below with reference to FIGS. 1 to 8. A two-shaft worm machine 1 configured as a two-shaft extruder has a housing 2 consisting of a plurality of housing portions 3, 4, 5, 6 arranged one behind the other and designated housing sections. Configured in the housing 2 are a first housing bore 7 and a second housing bore 8 penetrating the latter, the associated axes 9, 10 of which run parallel to one another. In the penetration region of the housing bores 7, 8, the housing portions 3 to 6 have an upper first interstice 11 and a correspondingly configured lower second interstice 12.

Shafts 13, 14, which can be rotatably driven by a drive motor 15, are arranged in the housing bores 7, 8 concentrically with respect to the respectively associated axis 9, 10. A branch gearing 16 is arranged between the shafts 13, 14 and the drive motor 15, a clutch 17 being in turn arranged between the drive motor 15 and the branch gearing 16. The shafts 13, 14 are driven in the same direction, in other words in the same rotational directions 18, 19 about the axes 9, 10. The axes 9, 10 are accordingly also designated rotational axes.

Arranged on the first housing portion 3 adjacent to the branch gearing 16 is a material feed 20 in the form of a funnel, through which plastics material to be prepared or processed can be fed into the housing bores 7, 8. The material is conveyed in a conveying direction 21 from the first housing portion 3 to the last housing portion 6 through the housing 2 and leaves the worm machine 1, for example, through a nozzle plate 22 closing off the housing 2.

The worm machine 1, one behind the other in the conveying direction 21, has a feed zone 23, a melting zone 24, a mixing zone 25 and a pressure build-up zone 26. Arranged on the shafts 13, 14 configured as toothed shafts are—one behind the other in the conveying direction 21 respectively associated with one another pair-wise, first worm elements 27, 28, first kneading elements 29, 30, second kneading elements 31, 32 and second worm elements 33, 34, in each case as treatment elements. Both the worm elements 27, 28, 33, 34 and the kneading elements 29, 30, 31, 32 mesh with one another, in other words are configured to be tightly meshing. The worm elements 27, 28 arranged next to one another pair-wise in each case form a first treatment element group 35. Accordingly, the kneading elements 29, 30 or 31, 32 and the worm elements 33, 34, in each case pair-wise, form further treatment element groups 36, 37 and 38.

A treatment element group 37 consisting of the kneading elements 31, 32 will be described in detail below with the aid of FIGS. 3 to 8. Only one treatment element group is shown in FIGS. 3 and 4 for reasons of clarity. The kneading elements 31, 32 of the following treatment element groups 37, for example, have an offset angle about the respective longitudinal axis M of 30°. The kneading elements 31, 32 are configured to be single-threaded and congruent with respect to one another. This means that the kneading elements 31, 32 can be made congruent by displacement and/or rotation about their respective longitudinal axis M₁ or M₂. The longitudinal axes M₁ and M₂ are concentric with respect to the associated rotational axes 9, 10 of the shafts 13, 14. In a cross sectional plane running perpendicular to the longitudinal axes M₁, M₂, the kneading elements 31, 32 in each case have an outer contour A₁(φ), A₂(φ) running about the associated longitudinal axis M₁, M₂, wherein φ is the angle about the respective longitudinal axis M₁, M₂ and is between 0≦φ≦360°. As the kneading elements 31, 32 are congruent with one another, their outer contours A₁(φ) and A₂(φ) are identical. Inasmuch as it is unimportant to distinguish the outer contours A₁(φ) and A₂(φ) below and the longitudinal axes M₁ and M₂, these are designated together by A(φ) or M.

The outer contours A(φ) have, relative to their respective longitudinal axis M, which serve as centre points, a minimum core radius R_(i) and a maximum outer radius R_(a). The outer radius R_(a) is smaller by a radial play <S_(r)> than the inner radius R_(b) of the housing bores 7, 8. As the kneading elements 31, 32 are configured to be tightly meshing, the sum of the core radius R_(i) and the outer radius R_(a) substantially equals the axial spacing a of the rotational axes 9, 10. This substantially means that a slight axial retraction b is disregarded. If this is taken into account, the sum of the core radius R_(i) and the outer radius R_(a) is equal to the difference of the axial spacing a and axial retraction b. The axial retraction b is disregarded below.

The construction of the outer contours A(φ) and their course will be described in detail below. The outer contours A(φ) have a spacing D_(A)(φ) from their longitudinal axis M, in each case, for which there applies in each case: R_(i)≦D_(A)(φ)≦R_(a). The outer contours A(φ) have a crest A(Δφ_(K)), a base A(Δφ_(G)) and two flanks A(Δφ_(F1)) and A(Δφ_(F2)). The angle portions Δφ_(K), Δφ_(G) and Δφ_(F) are designated the crest angle, base angle and flank angle. This is illustrated in FIG. 8.

The first flank A(Δφ_(F1)) is composed of a first outer contour portion A(Δφ₁) with an angle portion Δφ₁ and a transition portion A(Δφ_(T)) with a transition angle Δφ_(T) and forms an active flank of the kneading element 31, 32 in the respective rotational direction 18, 19. The second flank A(Δφ_(F2)) corresponds to a second outer contour portion A(Δφ₂) with an angle portion Δφ₂ and forms a passive flank of the kneading element 31, 32 lying counter to the respective rotational direction 18, 19. The outer contour portions A(Δφ₁) and A(Δφ₂) have a continuously changing distance D_(A)(Δφ₁) and D_(A)(Δφ₂) from the respective longitudinal axis M, for which in each case R_(i)<D_(A)(Δφ)>R_(a). This is illustrated in FIG. 7.

The outer contour portions A(Δφ₁) and A(Δφ₂) have an associated evolute E, which is a quantity of three points P(i), wherein i=1 to 3. The points P(i) lie outside the respective longitudinal axis M and inside the outer radius R_(a).

The construction of the outer contour portions A(Δφ₁) and A(Δφ₂) is illustrated in FIG. 6. To speak figuratively with respect to the construction thereof, a notional rod with the length of the axial spacing a is unwound on the evolute E, the first rod end defining the first outer contour portion A(Δφ₁) of one kneading element 31 and the second rod end defining the second outer contour portion A(Δφ₂) of the other kneading element 32 and vice versa. In other words, the notional rod is unrolled on a polygon course formed by the point P (1) to P(3), wherein the rod ends lie on the core radius R_(i) or the outer radius R_(a) at the beginning. The unrolling is ended when the rod end originally lying on the core radius R_(i) impinges on the outer radius R_(a). Unrolling is taken to mean that the notional rod is rotated about the point P(1) until the rod impinges on the next point of the polygon course, in other words on P(2). The notional rod is then rotated about the point P(2), until the rod impinges on the next point, in other words P(3). The notional rod is then rotated about the point P(3) until the rod end impinges on the outer radius R_(a). This unrolling is illustrated in FIG. 6, the notional rod being shown in individual positions while the unwinding is shown by dashed lines.

The outer contour portions A(Δφ₁) and A(Δφ₂) are therefore formed by three circular arcs, the associated centre points of which are the points P(1) to P(3). Adjacent points of the points P(1) to P(3) have a constant spacing Δr(i)=Δr from one another. This means that the radii of adjacent circular arcs, which are also called involute curves E′(1) to E′(3), differ by the spacing Δr(i)=Δr. The spacing Δr is less than R_(i) and less than R₁/2. In particular, the spacing Δr may also be smaller than R_(i)/4, in particular smaller than R_(i)/6, and, in particular, smaller than R_(i)/8. The circular arcs belonging to the points P(1) to P(3) have constant angles at centre Δε(i)=Δε. The angles at centre Δε(i)=Δε are less than 60°. In particular, the angle at centre Δε can also be smaller than 45° and in particular smaller than 30°.

Because of the constant spacings Δr and the constant angles at centre Δε, the points P(1) to P(3) lie on a continuous and differentiable curve in the form of a circle, which has a direction of curvature remaining the same.

FIG. 7 illustrates the further construction of the first flank portion A(ΔφF₁). The first flank portion A(Δφ_(F1)) is composed of the first outer contour portion A(Δφ₁) and the transition portion A(Δφ_(T)) with the transition angle Δφ_(T). The transition portion A(Δφ_(T)) is a circular arc about the centre point M_(T) with the transition radius R_(T). The centre point M_(T) is produced from the contact point of the outer radius R_(a) and the second outer contour portion A(Δφ₂). The transition radius R_(T) corresponds to the axial spacing a. To speak figuratively, the notional rod with the length of the axial spacing a—once the rod end impinges on the outer radius R_(a)—is pivoted about this contact point, in other words about the centre point M_(T), until the rod crosses the longitudinal axis M. The movable rod end then comes to rest on the core radius R_(i).

FIG. 8 illustrates the construction of the crest A(Δφ_(K)) and the base A(Δφ_(G)). The crest A(Δφ_(K)) is a circular arc with the longitudinal axis M as the centre point and a radius corresponding to the outer radius R_(a). The base A(Δφ_(G)) is also a circular arc with the longitudinal axis M as the centre point and a radius corresponding to the core radius R_(i). To speak figuratively, the notional rod, once this has impinged on the longitudinal axis M, is rotated about the latter, until the rod ends again impinge on their starting points. The crest angle Δφ_(K) therefore corresponds to the base angle Δφ_(G).

As the rod ends in each case define one of the outer contours A₁(φ) or A₂(φ), the process described has to be repeated again in order to define the complete outer contour A₁(φ) or A₂(φ) for each of the kneading elements 31, 32. Because of the fact that the outer contour portions A(Δφ₁) and A(Δφ₂) are formed on a common evolute E or have a common evolute E, the outer contours A₁(φ) and A₂(φ) resulting from the construction process are congruent. This means that the construction process described above does not have to be repeated for this special case, as both kneading elements 31, 32 are already constructed thereby.

The outer contour portions A(Δφ₁) and A(Δφ₂) are curved over their respective angle portions Δφ₁ and Δφ₂ and have no straight part portions. Moreover, the outer contours A₁(φ) or A₂(φ) have a uniform direction of curvature.

As can be seen from FIGS. 3 and 4, the evolutes E which are the same and associated with the kneading elements 31, 32 can be moved into one another by a linear displacement by the axial spacing a in the direction thereof. The sum of the spacings of the evolutes E or the curves, on which the points P(i) of the evolutes E lie, from the contact point B in the direction of the axial spacing a in each rotational position is substantially equal to the axial spacing a, whereby the kneading elements 31, 32 are tightly meshing.

The wedge K_(a) between the inner contour of the housing bores 7, 8 and the active flank A(Δφ_(F1)) and the corresponding wedge K_(p) between the inner contour of the passive flank A(Δφ_(F2)) can be flexibly adjusted in the kneading elements 31, 32 according to the invention, whereby the shear and/or extensional flows can be optimally adapted to the plastic material to be processed. The active angle α_(a) of intersection of the crest A(Δφ_(K)) and the active flank A(Δφ₁) is 0°. The passive angle α_(p) of intersection of the crest A(ΔφK) and the passive flank A(Δφ_(F2)) is greater than 0°.

Since the spacing of the evolutes E of the kneading elements 31, 32 in every rotational position corresponds to the axial spacing a, the kneading elements 31, 32 are tightly meshing and have a common tangent in their respective contact point B.

A second embodiment of the invention will be described below with reference to FIG. 9. In contrast to the previous embodiment, the treatment elements 31 a, 32 a are configured as worm elements. The outer contours A₁(φ) and A₂(φ) correspond to the first embodiment, wherein the latter are screwed along the respective rotational axis 9, 10 with a constant and continuous function. With regard to the further mode of functioning, reference is made to the first embodiment.

A third embodiment of the invention will be described below with reference to FIGS. 10 and 11. The kneading elements 31 b and 32 b are neither congruent with respect to one another nor symmetrical. The kneading elements 31 b, 32 b in each case have two evolutes E_(j), wherein j=1 and 2. Each of the evolutes E_(j) is a quantity of 3 points P_(j)(i) wherein I=1 to 3. The first evolute E₁ is a polygon course formed from the points P₁(1) to P₁(3), adjacent points of the points P₁(1) to P₁(3) having different spacings Δr(i). The second evolute E₂ corresponds to that of the first embodiment. The outer contour portions A₁(Δφ₁₁) and A₂(Δφ₁₂) are formed by unwinding the notional rod at the first evolute E₁. In accordance with the first embodiment, the transition portion A₁(Δφ_(T1)) is then formed by pivoting the notional rod about the centre point M_(T1). By rotating the notional rod about the centre point M, the crest A₂(Δφ_(K2)) and the base A₁(Δφ_(G1)) are then formed in accordance with the first embodiment.

A further half rotation of the notional rod now follows. The notional rod is firstly unwound on the second evolute E₂, so the outer contour portions A₁(Δφ₂₁) and A₂(Δφ₂₂) are formed. By pivoting the notional rod about the centre point M_(T2), the transition portion A₂(Δφ_(T2)) is then formed analogously to the first embodiment. By rotating the notional rod about the centre point M, the base A₂(Δφ_(G2)) and the crest A₁(Δφ_(K1)) are formed and the outer contours A₁(φ) and A₂(φ) are closed. The outer contour portions A₁(Δφ₁₁) and A₂(Δφ₁₂) are therefore produced on the evolute E₁, whereas the outer contour portions A₁(Δφ₂₁) and A₂(Δφ₂₂) are produced on the evolute E₂ that is different therefrom. Accordingly, the wedges K_(a1) and K_(a2) or the wedges K_(p1) and K_(p2) and the angles α_(a1) and α_(a2) of intersection or the angles α_(p1) and α_(p2) of intersection are also configured differently. With regard to the further mode of functioning and construction, reference is made to the previous examples.

A fourth embodiment of the invention will be described below with reference to FIGS. 12 to 15. In contrast to the previous examples, the evolute E is a continuous and differentiable curve in the form of a circular arc about the centre point M_(E). Viewed mathematically, this evolute E can be formed in that a limit transition toward zero is carried out for the angle at centre Δε in accordance with the first embodiment. The spacing Δr of the points P(i) then passes into the arc length ds and the angle at centre Δε passes into the change of the tangent direction dε. The evolute E therefore has the radius of curvature R_(E)=ds/dε. The evolute E is therefore a circular arc with an infinite number of points P(i), wherein i=1 to ∞ in the limit transition. The construction of the flanks A(Δφ_(F1)) and A(Δφ_(F2)) according to FIGS. 13 and 14 takes place in accordance with the first embodiment, wherein the evolute E—as already stated—is a circular arc. As the outer contour portions A(Δφ₁) and A(Δφ₂) have the same evolute E, the kneading elements 31 c and 32 c are congruent with respect to one another. The kneading elements 31 c and 32 c are, however, non-symmetrical. The active angle of intersection α_(a)=0°. Accordingly, the passive angle of intersection α_(p)>0°. The wedges K_(a) and K_(p) can thus be flexibly adapted to the plastics material to be processed. With regard to the further mode of functioning and construction, reference is made to the previous embodiments.

A fifth embodiment of the invention will be described below with reference to FIG. 16. The kneading elements 31 d and 32 d are configured in accordance with the fourth embodiment and have an evolute E, which is a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R_(a) to the core radius R_(i) equals 1.55. The crest angle Δφ_(K)=20° and the active angle of intersection α_(a)=0°. The passive angle of intersection α_(p)>0°. The associated wedges K_(a) and K_(p) can thus be flexibly adapted to the plastics material to be processed. Reference is made to the preceding examples with regard to the further mode of functioning and construction.

A sixth embodiment of the invention will be described below with reference to FIG. 17. The kneading elements 31 e and 32 e are configured in accordance with the fourth embodiment and have an evolute E, which is a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R_(a) to the core radius R_(i) equals 1.55. The crest angle Δφ_(K)=80°. The active angle of intersection α_(a)=0°. The passive angle of intersection α_(p)>0°. The associated wedges K_(a) and K_(p) can thus be flexibly adapted to the plastics material to be processed. With regard to the further mode of functioning and construction, reference is made to the previous embodiments.

A seventh embodiment of the invention will be described below with reference to FIG. 18. The kneading elements 31 f and 32 f are configured in accordance with the fourth embodiment and have an evolute E, which is a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R_(a) to the core radius R_(i) equals 1.55. The crest angle Δφ_(K)=20°. The active angle of intersection associated with the active flank A(Δφ_(F1)) is α_(a)=15°. The passive angle of intersection associated with the passive flank A(Δφ_(F2)) is α_(p)=20°. The associated wedges K_(a) and K_(p) can thus be flexibly adapted to the plastics material to be processed. With regard to the further mode of functioning and construction, reference is made to the previous embodiments.

An eighth embodiment of the invention will be described below with reference to FIG. 19. The kneading elements 31 g and 32 g are configured in accordance with the fourth embodiment and have an evolute E, which is a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R_(a) to the core radius R_(i) equals 1.55. The crest angle Δφ_(K)=20°. The active angle of intersection associated with the active flank A(Δφ_(F1)) is α_(a)=5°. The passive angle of intersection associated with the passive flank A(Δφ_(F2)) is α_(p)=10°. The associated wedges K_(a) and K_(p) can thus be flexibly adapted to the plastics material to be processed. With regard to the further mode of functioning and construction, reference is made to the previous embodiments.

A ninth embodiment of the invention will be described below with reference to FIG. 20. The kneading elements 31 h and 32 h are configured in accordance with the fourth embodiment and have an evolute E, which is a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R_(a) to the core radius R_(i) equals 1.55. The crest angle Δφ_(K)=20°. The active associated angle of intersection α_(a)=5°. The passive angle of intersection α_(p)=20°. The associated wedges K_(a) and K_(p) can thus be flexibly adapted to the plastics material to be processed. With regard to the further mode of functioning and construction, reference is made to the previous embodiments.

A tenth embodiment of the invention will be described below with reference to FIG. 21. The kneading elements 31 i and 32 i are configured in accordance with the fourth embodiment and have an evolute E, which is continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R_(a) to the core radius R_(i) equals 1.55. The crest angle Δφ_(K)=20°. The active angle of intersection α_(a)=10°. The passive angle of intersection α_(p)=10°. Because of the same angles α_(a) and α_(p) of intersection, the kneading elements 31 i and 32 i are congruent and symmetrical. The associated wedges K_(a) and K_(p) are configured the same. With regard to the further mode of functioning and construction, reference is made to the previous embodiments.

An eleventh embodiment of the invention will be described below with reference to FIG. 22. The kneading elements 31 j and 32 j are configured in accordance with the fourth embodiment and have an evolute E and a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R_(a) to the core radius R_(i) equals 1.55. The crest angle Δφ_(K)=0°. The crest A(Δφ_(K)) therefore degenerates to a single point, the centre point M_(T). The angle α_(a) of intersection associated with the active flank A(Δφ_(F1)) is maximal. The angle α_(p) of intersection associated with the passive flank A(Δφ_(F2)) is also maximal. Because of the same angles α_(a) and α_(p) of intersection, the kneading elements 31 j and 32 j are congruent and symmetrical. The associated wedges K_(a) and K_(p) can thus be flexibly adapted to the plastics material to be processed. With regard to the further mode of functioning and construction, reference is made to the previous examples.

A twelfth embodiment of the invention will be described below with reference to FIG. 23. The kneading elements 31 k and 32 k are configured in accordance with the fourth embodiment and have an evolute E and a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R_(a) to the core radius R_(i) equals 1.55. The crest angle Δφ_(K)=100°. The active angle α_(a) of intersection is maximal. The passive angle α_(p) of intersection is also maximal. Because of the same angles α_(a) and α_(p) of intersection, the kneading elements 31 k and 32 k are congruent and symmetrical. The passive flank A(Δφ_(F2)) is formed from the outer contour portion A(Δφ₂) and a further transition portion A(Δφ_(T2)), in contrast to the previous embodiments. The second transition portion A(Δφ_(T2)) is produced as a circular arc about the centre point M_(T2) with the transition radius R_(T), which corresponds to the axial spacing a. The associated wedges K_(a) and K_(p) may thus be flexibly adapted to the plastics material to be processed.

Reference is made to the previous embodiments with regard to the further mode of functioning and construction.

A thirteenth embodiment of the invention will be described below with reference to FIG. 24. The kneading elements 31 l and 32 l have two evolutes E₁ and E₂, which are configured in accordance with the fourth embodiment and are a continuous and differentiable curve in the form of a circular arc. The kneading elements 31 l and 32 l are accordingly not congruent, but symmetrical. The ratio of the outer radius R_(a) to the core radius R_(i) equals 1.55. The crest angle Δφ_(K)=0°. The crest A(ΔφK) therefore degenerates to a single point, the centre point M_(T). The angles α_(a1) and α_(p1) and α_(a2) and α_(p2) of intersection are the same, so the same wedges K_(a1) and K_(p1) and K_(a2) and K_(p2) are produced. With regard to the further mode of functioning and construction reference is made to the previous embodiments.

A fourteenth embodiment of the invention will be described below with reference to FIG. 25. The kneading elements 31 m and 32 m have two evolutes E₁ and E₂, which are configured in accordance with the fourth embodiment and are a continuous and differentiable curve in the form of a circular arc. The kneading elements 31 m and 32 m are accordingly not congruent, but symmetrical. The ratio of the outer radius R_(a) to the core radius R_(i) equals 1.55. The crest angle Δφ_(K)=120°. The angles α_(a1) and α_(p1) and α_(a2) and α_(p2) of intersection are the same, so the same wedges K_(a1) and K_(p1) and K_(a2) and K_(p2) are produced. The evolutes E₁ and E₂ have a common tangent T, so the outer contour portions A₁(Δφ₁₁) and A₁(Δφ₂₁) and A₂(Δφ₁₂) and A₂(Δφ₂₂) pass into one another in a continuous and differentiable manner. With regard to the further mode of functioning and construction, reference is made to the previous embodiments.

A fifteenth embodiment of the invention will be described below with reference to FIGS. 26 and 27. The kneading elements 31 n and 32 n are two-threaded. The kneading elements 31 n and 32 n have four evolutes E₁ to E₄, which are continuous and differentiable curves in the form of circular arcs. The kneading elements 31 n and 32 n are congruent. The outer contour A₁(φ) of the kneading element 31 n is composed of the outer contour portion A₁(Δφ₁₁) unwound on the evolute E₁, the outer contour portion A₁(Δφ₂₁) unwound on the evolute E₂, the transition portion A₁(Δφ_(T11)) about the centre point M_(T11), the outer contour portion A₁(Δφ₃₁) unwound on the evolute E₃, the outer contour portion A₁(Δφ₄₁) unwound on the evolute E₄ and the transition portion A₁(Δφ_(T21)) about the centre point M_(T21). The outer contour A₂(φ₂) of the kneading element 32 n is produced with the aid of the evolutes E₁ to E₄ accordingly, wherein the transition portions A₂(Δφ_(T12)) and A₂(Δφ_(T22)) have the centre points M_(T12) and M₂₂. The active angles α_(a1) and α_(a2) of intersection equal 0°. The passive angles α_(p1) and α_(p2) of intersection are the same and greater than 0°. Accordingly, the active wedges K_(a1) and K_(a2) and the passive wedges K_(p1) and K_(p2) are the same. With regard to the further mode of functioning and construction, reference is made to the previous embodiments.

A sixteenth embodiment of the invention will be described below with reference to FIG. 28. The kneading elements 31 o and 32 o are two-threaded in accordance with the fifteenth embodiment and have four evolutes E₁ to E₄ in the form of circular arcs. The kneading elements 31 o and 32 o are not congruent, but symmetrical. The outer contour A₁(φ) of the treatment element 31 o is composed of the outer contour portion A₁(Δφ₁₁) unwound on the evolute E₁, the crest A₁(Δφ_(K1)) about the centre point M₁, the outer contour portion A₁(Δφ₂₁) unwound on the evolute E₂, the outer contour portion A₁(Δφ₃₁) unwound on the evolute E₃, the crest A₁(Δφ_(K2)) about the centre point M₁ and the outer contour portion A₁(Δφ₄₁) unwound on the evolute E₄. The evolutes E₂ and E₃ and E₁ and E₄ in each case have a common tangent T₁ and T₂, so the outer contour portions A₁(Δφ₂₁) and A₁(Δφ₃₁) and A₁(Δφ₄₁) and A₁(Δφ₁₁) pass into one another in a continuous and differentiable manner. The outer contour A₂(φ) of the treatment element 32 o is formed in accordance with the evolutes E₁ to E₄, the outer contour portions A₂(Δφ₁₂) and A₂(Δφ₂₂) being connected by the base A₂(Δφ_(G1)) and the outer contour portions A₂(Δφ₃₂) and A₂(Δφ₄₂) by the base A₂(Δφ_(G2)). The active angle α_(a1) of intersection and the passive angle α_(p1) of intersection of the treatment element 31 o are about 33°. The active angle α_(a2) of intersection and the passive angle α_(p2) of intersection of the treatment element 32 o are 0°. Consequently, the wedges K_(a1) and K_(p1) are the same. The same applies to the wedges K_(a2) and K_(p2). With regard to the further mode of functioning and construction, reference is made to the previous embodiments.

With reference to FIG. 29, a seventeenth embodiment of the invention will be described below. The kneading elements 31 p and 32 p are two-threaded. The kneading elements 31 p and 32 p are not congruent, but symmetrical. The kneading elements 31 p and 32 p have four evolutes E₁ to E₄, which are, in each case, continuous and differentiable curves. The evolutes E₁ to E₄ form an astroid, which can be described by the following equations: x=c·(cos(t))^(n) y=d·(sin(t))^(n) with the factors c and d and the exponent n, wherein c>d and n=3. The outer contour A₁(φ) of the kneading element 31 p is composed of the outer contour portion A₁(Δφ₁₁) unwound on the evolute E₁, the outer contour portion A₁(Δφ₂₁) unwound on the evolute E₂, the outer contour portion A₁(Δφ₃₁) unwound on the evolute E₃ and the outer contour portion A₁(Δφ₄₁) unwound on the evolute E₄. The evolutes E₁ to E₄ in each case have, pair-wise, common tangents T₁ to T₄, so the outer contour portions A₁(Δφ₁₁) to A₁(Δφ₄₁) pass into one another in a continuous and differentiable manner. The outer contour A₂(φ) of the kneading element 32 p is comprised accordingly. The active angle α_(a1) of intersection and passive angle α_(p1) of intersection of the kneading element 31 p are the same, so the wedges K_(a1) and K_(p1) are also the same. The same applies to the active angle α_(a2) of intersection and passive angle α_(p2) of intersection and the corresponding wedges K_(a2) and K_(p2) of the kneading element 32 p. The angles α_(a2) and α_(p2) of intersection are, however, smaller than the angles α_(a1) and α_(p1) of intersection. The crests and bases of the kneading elements 31 p and 32 p are degenerated to single points. With regard to the further mode of functioning and construction, reference is made to the previous embodiments.

An eighteenth embodiment will be described below with reference to FIG. 30. The kneading elements 31 q and 32 q are triple-threaded. The kneading elements 31 q and 32 q are congruent and symmetrical. They have three evolutes E₁ to E₃, which are in each case continuous and differentiable curves and together form a tricuspoid. The outer contour A₁(φ) of the kneading element 31 q is composed of the outer contour portion A₁(Δφ₁₁) unwound on the evolute E₁, the outer contour portion A₁(A_(T21)) unwound on the evolute E₂, the outer contour portion A₁(Δφ₃₁) unwound on the evolute E₃ and the outer contour portions A₁(Δφ₄₁) to A₁(Δφ₆₁) formed with a corresponding unwinding process. As the evolutes E₁ to E₃ in each case have, pair-wise, a common tangent T₁ to T₃, the outer contour portions A₁(Δφ₁₁) to A₁(Δφ₆₁) pass into one another in a continuous and differentiable manner. The active angles α_(a1) and α_(a2) of intersection and the passive angles α_(p1) and α_(p2) of intersection are the same size, so corresponding wedges K_(a1), K_(a2), K_(p1) and K_(p2) are produced. The outer contour A₂(φ) of the kneading element 32 q is formed in accordance with the kneading element 31 q. With regard to the further functioning and construction, reference is made to the previous embodiments.

A nineteenth embodiment of the invention will be described below with reference to FIGS. 31 and 32. The kneading elements 31 r and 32 r are single-threaded. They are congruent, but not symmetrical. The kneading elements 31 r and 32 r have an evolute E, which is a continuous and differentiable curve in the form of a spiral. The spiral can be described by the equation ρ=k·t ^(n) wherein ρ is the radius, k is a constant and t is the angle (in polar coordinates) of the spiral. The kneading elements 31 r and 32 r have a crest angle Δφ_(K)=20°. The active angle of intersection α_(a)=0°. The passive angle of intersection α_(p1)>0°. The exponent n equals 2.5. The spiral-shaped evolute E is additionally rotated through 180°. With regard to the further mode of functioning and construction, reference is made to the previous embodiments, in particular the fourth embodiment.

A twentieth embodiment of the invention will be described below with reference to FIGS. 33 and 34. The kneading elements 31 s and 32 s are single-threaded and not congruent. The kneading elements 31 s and 32 s have two evolutes E₁ and E₂, which in each case form a continuous and differentiable curve in the form of a spiral. The crest angle Δφ_(K)=20°. Accordingly, the base angle Δφ_(G)=20°. The active angle of intersection α_(a1)=20°. The active angle of intersection α_(a2) equals 10°. The exponent n=1.0. The spiral evolutes E₁ and E₂ are rotated through 120° and 100°. With regard to the further mode of functioning and construction, reference is made to the previous examples, in particular the third and nineteenth embodiments.

A twenty-first embodiment of the invention will be described below with reference to FIG. 35. The kneading elements 31 t and 32 t are configured in accordance with the sixteenth embodiment. In contrast to the previous embodiments, the kneading elements 31 t and 32 t with their longitudinal axes M₁ and M₂ are arranged eccentrically with respect to the associated rotational axes 9 and 10. The longitudinal axes M₁ and M₂ therefore have a spacing e from the associated rotational axes 9 and 10, which characterizes the eccentricity. Because of the eccentric arrangement, the shape of the wedges K_(a1) and K_(p1) or wedges K_(a2) and K_(p2) and the size of the angles α_(a1) and α_(p1) or α_(a2) and α_(p2) of intersection depend on the rotational position of the kneading elements 31 t and 32 t. The spacing e along the rotational axes 9, 10 may be constant or vary. Moreover, the angle at which the kneading elements 31 t and 32 t are eccentrically moved out may be constant or vary. With regard to the further mode of functioning, reference is made to the previous embodiments. In particular, the treatment elements 31, 32 to 31 s, 32 s described in the previous embodiments may also be eccentrically arranged in accordance with the twenty first embodiment. 

The invention claimed is:
 1. A treatment element for treating material in a multi-shaft worm machine, comprising a longitudinal axis M, a respective core radius R_(i) having the longitudinal axis M as the centre point and an outer radius R_(a), an outer contour A(φ) running about the longitudinal axis M, wherein φ is the angle about the longitudinal axis M and R_(i)≦D_(A)(φ)≦R_(a) applies to a spacing D_(A)(φ) of the outer contour A(φ) from the longitudinal axis M, wherein the outer contour A(φ) has at least one outer contour portion A(Δφ), which runs along an angle portion Δφ, which has a continuously changing spacing D_(A)(Δφ) from the longitudinal axis M, wherein R_(i)<D_(A)(Δφ)<R_(a), and which has an associated evolute E, which is a quantity of n points P(i) where i=1 to n and n≧3, wherein each of the points P(i) lies outside the longitudinal axis M and within the outer radius R_(a), and wherein two respective adjacent points P(i) and P(i+1) have the spacing Δr(i) from one another, which is less than R_(i)/2.
 2. A treatment element according to claim 1, wherein two respective adjacent points P(i) and P(i+1) have a spacing Δr(i) from one another, which is less than R_(i)/4, the two respective adjacent points P(i) and P(i+1) belonging to adjacent involute curves E′(i) and E′(i+1).
 3. A treatment element according to claim 1, wherein two respective adjacent points P(i) and P(i+1) have a spacing Δr(i) from one another, which is less than R_(i)/6, the two respective adjacent points P(i) and P(i+1) belonging to adjacent involute curves E′(i) and E′(i+1).
 4. A treatment element according to claim 1, wherein two respective adjacent points P(i) and P(i+1) have a spacing Δr(i) from one another, which is less than R_(i)/8, the two respective adjacent points P(i) and P(i+1) belonging to adjacent involute curves E′(i) and E′(i+1).
 5. A treatment element according to claim 1, wherein two respective adjacent points P(i) and P(i+1) have a constant spacing Δr from one another.
 6. A treatment element according to claim 1, wherein the involute curves E′(i) belonging to the points P(i) in each case have an angle at centre Δε(i), which is less than 60°.
 7. A treatment element according to claim 1, wherein the involute curves E′(i) belonging to the points P(i) in each case have an angle at centre Δε(i), which is less than 45°.
 8. A treatment element according to claim 1, wherein the involute curves E′(i) belonging to the points P(i) in each case have an angle at centre Δε(i), which is less than 30°.
 9. A treatment element according to claim 1, wherein the involute curves E′(i) belonging to the points P(i) have constant angles at centre Δε.
 10. A treatment element according to claim 1, wherein the points P(i) lie on a continuous and differentiable curve, which has a direction of curvature that remains the same.
 11. A treatment element according to claim 10, wherein the evolute E is equal to the curve, at least in portions.
 12. A treatment element according to claim 1, wherein the at least one outer contour portion A(Δφ) is curved over the entire angle portion Δφ.
 13. A treatment element according to claim 1, wherein the outer contour A(φ) has at least two outer contour portions A(φ₁) and A(φ₂).
 14. A treatment element according to claim 1, wherein the outer contour A(φ) has at least four outer contour portions A(φ₁) to A(φ₄).
 15. A treatment element according to claim 1, wherein the outer contour A(φ) has at least two outer contour portions A(Δφ_(j)) and A(Δφ_(j+i)), which have a common evolute E_(j).
 16. A treatment element according to claim 1, wherein the outer contour A(φ) has at least two outer contour portions A(Δφ_(j)) and A(Δφ_(j+1)) and the at least two associated evolutes E_(j) and E_(j+1) are different.
 17. A treatment element according to claim 1, wherein the outer contour A(φ) has at least two outer contour portions A(Δφ_(j)) and A(Δφ_(j+i)) and the at least two associated evolutes E_(j) and E_(j+1) have a common tangent (T).
 18. A treatment element according to claim 1, wherein the outer contour A(φ) has a uniform direction of curvature.
 19. A treatment element according to claim 1, wherein the outer contour A(φ) is multi-threaded.
 20. A treatment element according to claim 1, wherein the outer contour A(φ) is two-threaded.
 21. A multi-shaft worm machine with a housing, at least two housing bores, which penetrate one another and are parallel to one another, at least two shafts arranged concentrically in the housing bores, which are rotatably drivable about associated rotational axes, and which have an axial spacing a of the rotational axes, a plurality of treatment elements for treating material, which are non-rotatably arranged one behind the other in an axial direction on the at least two shafts, and which are configured to tightly mesh with one another, wherein at least two treatment elements arranged directly next to one another are configured such that each treatment element comprises a longitudinal axis M, a respective core radius R_(i) having the longitudinal axis M as the centre point and an outer radius R_(a), an outer contour A(φ) running about the longitudinal axis M, wherein φ is the angle about the longitudinal axis M and R_(i)≦D_(A)(φ)≦R_(a) applies to a spacing D_(A)(φ) of the outer contour A(φ) from the longitudinal axis M, wherein the outer contour A(φ) has at least one outer contour portion A(Aφ), which runs along an angle portion Δφ, which has a continuously changing spacing D_(A)(φ) from the longitudinal axis M, wherein R_(i)<D_(A)(Δφ)<R_(a), and which has an associated evolute E, which is a quantity of n points P(i) where i=1 to n and n≧3, wherein each of the points P(i) lies outside the longitudinal axis M and within the outer radius R_(a), and wherein two respective adjacent points P(i) and P(i+1) have the spacing, and the sum of the core radius R_(i) and the outer radius R_(a) substantially equals the axial spacing a.
 22. A multi-shaft worm machine according to claim 21, wherein the at least two shafts arranged concentrically in the housing bores are rotatably drivable in the same direction.
 23. A multi-shaft worm machine according to claim 21, wherein the evolutes E_(j) of the treatment elements arranged next to one another are movable into one another by linear displacement in the direction of the axial spacing a.
 24. A multi-shaft worm machine according to claim 23, wherein the linear displacement corresponds to the axial spacing a.
 25. A multi-shaft worm machine according to claim 21, wherein the longitudinal axes M of the treatment elements arranged next to one another are arranged eccentrically with respect to the associated rotational axes. 